G. Clausnitzer

Screening corrections to the Rutherford cross section

Abstract Differential cross sections for elastic p-Au scattering were measured in the energy range between 0.2 and 0.8 MeV for scattering angles from 30° to 150° in order to determine corrections to the Rutherford cross section due to the screening of the nuclear charge by the atomic electrons. Furthermore, differential cross sections have been calculated in the weakly screening region using various screening functions. A simple analytical expression has been derived for the representation of both experimental and theoretical results.

Proton and helium stopping cross sections in H2, He, N2, O2, Ne, Ar, Kr, Xe, CH4 and CO2

Abstract Proton and helium stopping cross sections were measured for the noble gases helium, neon, argon, krypton and xenon, the diatomic gases hydrogen, nitrogen and oxygen and for the molecules carbon dioxide and methane in the energy ranges 700 keV–2.1 MeV and 1.0–3.0 MeV, respectively. The statistical and systematical errors are between 1.0 and 1.5% each. Optimum parameters for the Andersen-Ziegler semi-empirical formula were deduced for all data sets by means of the least-squares method. From the stopping cross sections of protons and 4He-ions at same velocity higher order Z1 corrections (Barkas-correction) for the noble gases He, Ne, Ar, Kr and Xe and the diatomic gases H2, N2 and O2 were calculated, using theoretical values for the Bloch-correction approximated by Bichsel and Porter. The experimental Z13-corrections were compared with the different theoretical predictions of Ashley, Ritchi and Brandt, Jackson and McCarthy and Lindhard and Esbensen.

Phase-shift analysis of pd elastic scattering below break-up threshold

Abstract A phase-shift analysis was performed for pd elastic scattering based on measurements of differential cross sections and proton and deuteron analyzing powers for energies below the break-up threshold. The angular momenta were restricted to l ⩽ 3; j -splitting and channel-spin mixing of the P-phases and the tensor coupling between the S- and D-phases were taken into account. The phase shifts were parameterized by the effective-range formalism and the corresponding parameters were directly deduced from the data. The results are compared with Faddeev calculations in which the Coulomb interaction is treated exactly or as a two-body approximation.

Proton stopping powers in various gases

Abstract The proton stopping powers of H2, He, N2, O2, Ne, Ar, Kr and Xe were measured for proton energies between 60 and 800 keV with an accuracy of about 2%. The protons were scattered off a thin gold foil mounted in the center of a gas-filled scattering chamber. The energy loss in the gas is given by the shift of the elastic peak measured with and without gas filling. The experimental data were fitted using the semi-empirical five-parameter formula of Andersen and Ziegler. Shell corrections were calculated from the measured stopping powers and compared to the theoretical shell-correction calculations of Bonderup which are based on the Lindhard-Scharff model.

Proton and helium stopping cross sections in N2, O2, NO and N2O.

Proton and 4H stopping powers were measured for nitrogen, oxygen, nitric oxide and nitrous oxide in the energy ranges 50–2000 and 100–3000 keV, respectively. The statistical and systematical errors are between 1.0 and 1.5% each. Optimum parameters for the Andersen-Ziegler semiempirical formula were deduced for all data sets. The stopping power of atomic nitrogen was determined in a first approach with a modified Bragg-rule.

An electron beam ion source for the production of multiply charged heavy ions

Abstract An electron beam ion source for the production of multiply-charged heavy ions has been developed. Continuous ion beams of neon, argon, krypton, and xenon ions have been produced. Xenon beam currents are in the range from some 10−9 A for Xe10+ up to about 10−6A for charge states lower than q=4 (q=ionic charge state). The energy spread δE of the ion beam was measured to be δE≤q·50 eV, the emittance ϵ was estimated to be ϵ cm · rad (2 m · eV ) 1 2 . The ion source proved to be very reliable and simple to operate. There are no apparent problems that limit the lifetime of the source.

Differential cross section, analyzing power and phase shifts for p-3He elastic scattering below 1.0 MeV☆

Abstract Differential cross sections and analyzing powers for the elastic scattering of polarized protons by unpolarized 3 He nuclei have been measured at eight energies between 0.3 MeV and 1.0 MeV for scattering angles θ c.m. = 52.4°–173.3°. The cross-section values were normalized to the Rutherford cross section for proton-krypton scattering. The analyzing powers have been measured with a statistical accuracy of about 0.001. The phase-shift analysis based on these data included all phases for orbital angular momenta l ≦ 1 and the channel-spin mixing parameter for the P waves. An energy parametrization of the phase shifts by an effective-range approximation allowed a simultaneous utilization of all data.

The Giessen polarization facility: II. 1.2 MeV tandem accelerator☆

Abstract A small pressure insulated tandem accelerator with 600 kV terminal voltage was constructed for the application of a polarized ion source of the Lambshift type; thin carbon foils or gas stripping is used for the charge exchange in the high voltage terminal. The calculated ion optical properties were realized in the construction; transmission and energy resolution are sufficient to obtain high intensity polarized beams on target (maximum 0.6 μA protons with P = 0.75) for precision polarization experiments in the 0.2–1.2 MeV energy region.

Differential cross sections and analyzing powers for pd elastic scattering below 1.0 MeV

Abstract Differential cross sections for the elastic pd scattering were measured at seven energies between 0.4 and 1.0 MeV for scattering angles from θc.m. = 44.5° to 149.2°. A mixture of D2 and Kr was used as target gas and the pd differential cross sections were determined relative to those of pKr scattering with a statistical error of Δσ σ ∼5 × 10−3. Analyzing powers for p d scattering were measured at 0.8, 0.9 and 1.0 MeV with a statistical error of ΔAy ∼5 × 10−4.

4He stopping cross sections in H2, He, N2, O2, Ne, Ar, Kr, e, CH4 and CO2

Abstract Helium stopping powers were measured for ten gases in the energy range between 0.1 and 1.1 MeV with a total accuracy of about 2.5%. Additionally, the proton stopping powers in CO 2 and CH 4 were determined. Optimum parameters for the Andersen-Ziegler semi-empirical formula were deduced for all data sets by means of the least-squares method. Stopping-power ratios S He / S p were determined using proton stopping powers for H 2 , N 2 , O 2 and the five inert gases which were measured recently with the same experimental set-up; they show a strong dependence on the target atomic number. The low-energy helium stopping cross sections were filted to the power function S = kE p . Experimental shell corrections were deduced from the measured helium stopping powers and compared with the theoretical shell corrections of Bonderup, whereby different higher-order Z l correction terms were included. The results show that in the energy range investigated it is not possible to obtain a consistent description for all gases.